We can not create object of abstract class, but inherit class and use methods of abstract class.

abstract class testParent {
public function abc() { //body of your funciton }
}
class testChild extends testParent {
public function xyz() { //body of your function }
}
$a = new testChild();

Abstract functions(methods) are those functions of abstract class which is only defined. It will be declared in child class.

abstract class abc { abstract protected function f1($a , $b); }
class xyz extends abc {
protected function f1($name , $address) { echo "$name , $address"; }
}
$a = new xyz();